I. Field
The present disclosure relates generally to coating lenses, and more specifically to techniques and devices useful in providing coatings to ophthalmic lenses.
II. Background
Ophthalmic lenses made out of organic materials (also called plastic lenses) are currently employed in a variety of eyeglasses, safety goggles, and the like. Such lenses are very lightweight, fabricated from materials such as polycarbonate, and have virtually replaced other materials such as glass. However, while modern ophthalmic lenses are durable and light, a significant issue with plastic ophthalmic lenses is scratch resistance, and for this reason virtually all ophthalmic lenses are coated with a hard coating, frequently a urethane based coating that is typically reactive to ultraviolet (UV) light.
Certain procedures have been developed that apply hard coatings to ophthalmic lenses, but these procedures and systems suffer from two major drawbacks: they tend to be labor intensive and/or tend to direct air or some other gas toward the lens for drying purposes, both of which are undesirable. Certain machines have been developed to automate the process, but in some instances, particularly with specialty glasses or small producers of such lenses, an operator is required to position the lenses, typically on a support that at least partially obscures an edge or a side of each lens, coat the lenses, reposition the lenses such that the region supported is coated, and coat the remaining side of each lens. The coated lens must be dried in some manner, possibly at multiple times during the procedure, and air pressure drying is typically employed. The problem with this procedure is that an operator must perform each of these steps, and they can be time consuming, and lenses output per hour can be limited. Further, when repositioning the lenses, the coating can pick up small particles and if the particles dry within the coating a lens can be deemed useless. Thus the need to reposition and dry multiple times is potentially problematic and costly.
Further, whether the lenses are positioned manually by an operator or by an automated process, they are dried using a gas, typically air but different types of gases have been employed (oxygen, etc.), expelled in the direction of the coated lens or lenses for a period of time, resulting in a dry product. Compressed gasses can be problematic, resulting in small particles being blown over the coatings with the gas when drying or curing the coating. While compressed gasses can be of varying qualities and purities, such gasses are never completely free of particulates, and in some cases can include a significant number of particulates. Further, other sources of particles may exist, including but not limited to particles generated by pneumatic cylinders, control valves, and vacuum generators. With respect to compressed gasses, the cost of compressed gasses tends to correlate with quality, but even the highest quality compressed gas is not particulate free. As with the repositioning discussed above, providing gas containing small particles over coatings can result in such particles sticking to the coatings, which when dried result in an unacceptable lens. Once the coating is dried, it is very difficult or impossible to be removed from the ophthalmic lens, and imperfections in eyeglasses and goggles are simply unacceptable.
Additionally, the friction of blown gasses can generate surface static electrical charges, and directing gases toward or across a lens can result in a small charge being applied to the lens or coated lens, which may draw fine particles to the lens. This too is undesirable, and thus techniques other than directing gasses toward the lens can provide benefits to the overall lens coating process.
A process and/or device that reduces or eliminates ophthalmic lens coating issues such as necessity for an operator and/or air drying issues is thus desirable.